Drum brake



Maul: 25, 1941. G. R. G. GATES DRUM BRAKE Filed Jan. 5, 1940 z zaanrg zMY I d ty Patented Mar. 25, 1941 I UNITED STATES PATENT OFFICE DRUM BRAKE Geoifrey Robert Greenbergh Gates, London, England, assignor to Automotive Products Company Limited, London, England Application January 5, 1940, Serial No. 312,583

In Great Britain January 28, 1939 4 Claims. (01. 185-78) Thisinvention relates to drum brakes of the lengthening of the shoe comprises a wedge memkind comprising a plurality of rigid arcuate shoes her which is carried by the shoe and is arranged which are supported upon a back plate or equivato be moved in a direction substantially parallel lent fixed part of the brake, and are arranged to with the drum axis, said wedge member conbe moved outwards into engagement with the veniently engaging slidably between relatively drum by spreading means. inclined surfaces formed respectively upon the It is the object of the present invention to protwo parts of the shoe. Thus the wedge member vide an improved form and construction of admay be interposed between the two parts of justing device which is so arranged that the the brake shoe so that said wedge member re- I m shoe is maintained in eflicient co-operation with ceives braking and/or brake-applying force from the spreading means and an anchorage device one member and transfers it directly to the other during all stages of lining wear. The invention member. The wedge member is preferably acis intended more particularly for use with brakes tuated by a screw having a head or equivalent in which the ends of the shoes are formed with which is located against axial movement relaconcave part-cylindrical surfaces which are tive to the two parts of the shoe, said screw if adapted to co-operate sl'idably with the anchordesired being arranged to engage with a screw age means so as to constitute in effect a pivotal thread in the wedge member and having its head mounting for the shoe end. or equivalent formed with a part-spherical sur- In an internal shoe drum brake a shoe is proface engaging a corresponding surface carried vided having its ends in engagement with an by the brake shoe, so as to allow said screw to 20 applying means and an anchorage respectively, take up a position determined by the wedge and the present invention is characterised by member. In the preferred construction the the fact that said ends are formed upon two wedge member is adapted to extend into an apermutually separate members which are held in ture formed in the web portion of the one part overlapping relationship and are adjustable upon of the shoe, and the other or terminal part of 25 one another to change the eifective length of said shoe is thickened at its inner end so that the shoe and thereby compensate for lining wear. it also extends into said aperture, the wedge Thus in an internal shoe drum brake includmember being formed with a sloping surface ing a rigid arcuate shoe having a circumferenwhich, in addition to bringing about the adjusttial flange portion fitted With e us n n ment of the shoe parts, also holds the said parts 30 material, the invention is further characterised together under the action of the forces in the by the fact that the shoe is provided with a tershoe when the brake is applied. Further, the minal member which forms one end of the shoe terminal member has its outer surface arcuateand is adjustable relatively to the main part of 1y curved so as to fit snugly within the flange 5 the shoe in a circumferential sense, said terportion of t main part of t brake Shoe min? membir havmg i inner end adjustably The improved adjusting device is particularly coPnected whh the mam a of w h and suitable for use in two-shoe brakes where each bang arranged to engage W the mtenor of the shoes is formed at each end with an arcu facel 9 i under e efiect Of the Shoe ate recess arranged to abut against and engage app pivotally with the fixed housing of the corre- 40 According to a still further feature of the 1nf f t d vention an internal shoe drum brake is prospondmg 0 pan lame pcaly oppose vided having a pair of rigid arcuate shoes of shoe'applymg. devlces having a T-shape in radial section, each shoe being arfloatmg actlon Yvhlch devmes are i i ously actuated during the normal application of ranged to bear at one end against a fixed abutk h b t ment or an applying device and carrying at its the bra 6 so t at h Shoes operate In lead other end a terminal member which is shaped mg Sense during each direction of nation of to lie against the internal surface of the shoe the drum flange, and has its inner end adjustably held to A brake of thls now be descnbed as the shoe Web whereby the adjustable holding an example of the invention with reference to 5 means acts as a stop for the terminal member the mp ying drawing, Which! so that as the latter is subjected to the shoegur 1 s a S de e a n of a brake assemapplying force, said member engages firmly with bly shown partly in section; the interior of the flange portion of the shoe. Figure 2 is a fragmentary sectional plan taken Preferably adjusting means for bringing about on the line 2-2 of Figure l; and

Figure 3 is a fragmentary side elevation corresponding to Figure 2 when seen in the direction of the arrow A, the back plate being removed.

A circular back plate I serves to support the non-rotating parts of the brake, namely a pair of actuating devices II and I2 and a pair of shoes indicated at I3 and I4, these latter being adapted to be spread apart into engagement with a rotatable cylindrical brake drum shown in section at I5. The two shoes I3 and I4 are of identical construction, so that only the shoe I4 will be described in detail. It comprises a main part which is of T shape in cross section and is formed with an arcuate flange I-6 carrying a lining I! in the customary manner. The central limb of the T section constitutes a web I8, and this is shaped at one end with a concave curved. surface I9 adapted to mate pivotally with a corresponding curved surface 28 upon the body of the actuating device I2. The web I8 is thickened by the provision of one or more reinforcing pilates 2| and the shoe is located against lateral displacement by a plate 22 forming part of the actuating device I2. The latter can be of any convenient form, and in the present example each of said actuating devices II and I2 is provided with a pair of hydraulic pistons indicated at 23, 24, 25 and 26. these having packing cups 21, The spaces between the pairs of pistons are fed in common from a master cylinder unit (not shown) or other suitable source of pressure liquid, so that the pistons 23, 24, 25 and 26 tend to be pushed outwards and thus spread the shoes I 3 and I4 into contact with the drum I5. 'I'he actuating devices are, however, essentially of a floating nature, for it will be appreciated that the pistons 23 and 24 .or 25 and 26 do not necessarily have to move to equal extents when the brake is applied.

The opposite end of the shoe .I4 is provided with a terminal member 28, which is generally of arcuate shape and is formed at its extremity with a concave curved surface 29 adapted to engage pivotally with the corresponding surface 38 of the actuating device I I. The outer curved surface 3| of the terminal member 28 is of such radius that it fits snugly against the interior of the flange i6, while a nut and bolt 32 having a spring washer passes through a slot 33 in the web I8 and fricti-onally holds the terminal member 28 against the main part of the shoe I4 without unduly restricting the sliding movement of these two parts. The terminal member 28 is formed with a pair of strengthening ribs 34 and 35.

The means used for locating the terminal member 28 in relation to the web l8 will be seen more clearly in Figures 2 and 3, and comprises a wedge member 36 which is screw-threaded at 31 for c-o-operation with a screw 38. The latter is formed with a flange 39 serving as a head, this having a part-spherical surface 40, While a bridge member 4I bearing against the web I8 has a corresponding concave surtac 42 so as to enable the flange or head 39 to seat properly. A friction washer 43 is positioned between the concave surface 42 and the surface 40 of the head or flange 39 so that the axial tension created in the screw 38 by the action o-fthe Wedge member 36 locks the adjustment against the efiects of vibration. A thin sheet metal plate 44 formed with a resilient detent 4-5, as will be seen in Figure 3, is secured to the bridge member 4| by welding or riveting. 'Th'ls detent is bent as shown to engage with a series of notches 46 formed in the flange or head 39 so as to locate the screw 38 and also give an audible indication of the extent to which said screw is rotated during adjustment of the brake shoe. The screw 38 has an extension 41 which is squared at its extremity for the engagement of a spanner, said extension 4'! being arranged to pass through :a slot 48 in the back plate I6 so as to permit the requisite movements of the brake shoe I4. The wedge member 36 is arranged as shown to extend through an aperture 49 in the web I8 and is formed with a surface 50 extending parallel with the axis of the .screw 38, said surface being adapted to slide upon the interior of the said aperture 49 as the screw 38 is rotated. An oblique surface I upon the wedge member 36 engages with a corresponding surface 52 upon the end of the terminal member 28, so that tightening of the screw 38 pulls the wedge member 36 through the aperture 4 9 and causes the terminal. member 28 to slide upon the web I8, thus increasing the effective length of the shoe I 4. The end of the terminal member 28 is thickened as indicated at 53 so as to extend into the aperture 49. The shoe I3 also provided with a terminal member 2-8, which is held against the Web I8 of said shoe by a locating nut and bolt 32 and a corresponding wedge member 36, the construction and operation of which are similar to those of the shoe I 4. The back plate I0 is fitted with a pair of studs 54 and 55 serving as anchorages for pull-off springs 56, 51 for the shoe I3 and 58, .59 for the shoe I4.

Wihen pressure liquid is fed to the actuating devices H and I2 while the drum I5 is rotating in, say, a clockwise direction, the shoes I3 and I4 are brought into contact with the drum and are carried round therewith until the curved surface I9 of the shoe I4 and the corresponding surface of the shoe I3, indicated at 60, engage with the fixed parts of the actuating devices I2 and II respectively. The opposite ends of the two shoes are in th meantime forced outwards against the drum by the pistons 24 and 25 so that both of the shoes I3 and I4 act in a leading sense. In a similar manner, during clockwise rotation of the drum I5 both shoes again act in a leading sense, the shoe I3 anchoring against the actuating device I2 and the shoe I4 anchoring with the fixed part of the actuating device II.

In all circumstances when the brake is applied the forces acting on each shoe tend to shorten the effective length of the shoe by causing the terminal member 28 to slide upon the web I8. This tendency is, however, efficiently resisted by the wedge member 36, which latter is gripped between the end of the terminal memher and the edge of the aperture 48 so that force is efiiciently transmitted from one part of the shoe to the other without straining the adjust ing screw 38. The inclination of the wedge surface 5| is arranged in such a sense that the terminal member 23 is at all times pressed firmly against the web I8, and of course the applying force and the braking force received by the just the clearance between the linings of the brake shoes l3, l4 and the drum l5.

I claim:

1. An internal shoe drum brake comprising a pair of rigid arcuate shoes of T-shape in radial section, a non-rotatable back plate, a pair of diametrically opposed double-acting shoe-applying devices having a floating action, which devices: comprise fixed housings and are simultaneously actuated during the normal application of the brake so that both shoes operate in a leading sense during each direction of rotation of the drum, a concave surface at one end of each shoe engaging pivotally with a convex surface upon the fixed housing of the adjacent applying device, a terminal member for each shoe arranged to lie against the shoe Web and to en gage with the interior of the flange of the shoe, said terminal member being shaped at its outer end with a concave surface engaging pivotally with the fixed housing of the other applying device, and adjusting means acting as a stop between the shoe and the terminal member, but arranged to shift the terminal member relative to the shoe for modifying the lining clearance.

2. An internal shoe drum brake comprising a rotatable drum, a non-rotatable back plate, a pair of rigid arcuate shoes each pivotally connected at one end with the back plate, said shoes being of T-shape in radial section with the web directed radially inwards, a frictional lining secured to the flange of each shoe, applying means mounted upon the back plate to urge the shoes into engagement with the drum, a terminal member operatively interposed between each shoe and the corresponding applying means, and wedge adjustment means mounted upon the shoe and arranged to cooperate with the end of the terminal member to shift said member alon the shoe and thus vary the lining clearance by modifying the effective length of the shoe measured from the pivot to the applying means, the terminal member being arranged with an outer curved edge which lies snugly in engagement with the interior surface of the brake shoe flange and is urged thereagainst by the force of the applying means.

3. An internal shoe drum brake according to claim 2, wherein the wedge adjustment means comprises a tapered block extending through an aperture in the shoe web, screw means for draw-- ing the block through the aperture, on surface of said block engaging slidably with the edge of said aperture and lying substantially at right angles to the shoe web, while the opposite surface is arranged obliquely and engages the end part of the terminal member, the said end part of the terminal member being thickened to provide an oblique surface which lies within the aperture and is disposed in the general plane of the shoe Web.

4. An internal shoe drum brake according to claim 2, wherein the wedge adjustment means comprises a wedge member, a screw threaded into said wedge member and having a head, and a member which is carried by the brake shoe and is arranged to engage with the under surface of the screw head, wherein said under surface of the screw head is of part-spherical shape and is arranged to mate with a corresponding partspherical concave surface formed in the member carried by the brake shoe.

GEOFFREY ROBERT qREENBERGI-I GATES v CERTIFICATE OF CORRECTION. Patent No. 2, 256,LL75. I 7 March 2 19in.

GEOFFREY ROBERT GREENBERGH GATES.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 5, second column, line 15, claim 5, for the word "on" before "surface" read oneand that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 29th day of April, A. D. l9L l.

Henry Van Arsdale,v

(Seal) Acting Commissioner of Patents. 

